Actuator and fluid pressure control circuit having the same

ABSTRACT

An actuator capable of preventing a malfunction of the actuator due to iron powder contained in working fluid and the abrasion of a cylinder and a piston is provided. The actuator includes a cylinder ( 51 ) extending in a vertical direction and having an opening ( 51   a ), a piston ( 52 ) moving inside the cylinder ( 51 ), and a stroke sensor ( 53 ) that detects a position of the piston ( 52 ). The stroke sensor ( 53 ) includes a member to be detected ( 53   b ) which is a magnet, and a sensor ( 53   c ) which detects the member to be detected ( 53   b ). The member to be detected ( 53   b ) is located below a lower edge portion ( 51   a   1 ) of the opening ( 51   a ).

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Japan application serial no. 2017-053775, filed on Mar. 17, 2017. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND Technical Field

The disclosure relates to an actuator that is provided as a part of a fluid pressure control circuit, and a fluid pressure control circuit including the same.

Description of Related Art

In the related art, as a hydraulic pressure control circuit (a fluid pressure control circuit) of a transmission that is mounted on a vehicle, a hydraulic pressure control circuit that controls a parking lock mechanism or the like by switching a supply destination of hydraulic pressure (fluid pressure) on the basis of a signal from a control unit (for example, see Patent Document 1) is known.

In the hydraulic pressure control circuit described in Patent Document 1, switching of a state of the parking lock mechanism is performed via an actuator provided as a part of a hydraulic pressure control circuit. An actuator to be used in this way includes an actuator including a cylinder, a piston that moves in an axial direction inside the cylinder according to supplied hydraulic pressure, and a stroke sensor that detects a position of the piston.

The stroke sensor includes a stroke sensor that calculates a position of a piston by attaching a magnet to the piston so that the magnet moves integrally with the piston and detecting a change in a magnetic force of the magnet.

-   [Patent Document 1] Japanese Unexamined Patent Application     Publication No. 2016-176589

Meanwhile, working fluid that is used in a fluid pressure control circuit as described in Patent Document 1 contains iron powder generated by abrasion of a clutch or the like. Therefore, there is a concern that the iron powder may be attached or attracted to the magnet of the stroke sensor of the actuator, and the iron powder attached or attracted to the magnet may flow into the cylinder when the piston of the actuator moves.

Thus, when the iron powder flows into the cylinder, there is a concern that a malfunction such as hindrance of the stroke of the piston may occur or abrasion of the cylinder and the piston may occur.

SUMMARY

The disclosure has been made in view of the above points, and the disclosure provides an actuator capable of preventing the malfunction of the actuator and the abrasion of a cylinder and a piston due to iron powder contained in working fluid is provided, and a fluid pressure control circuit including the actuator.

An actuator of the disclosure is an actuator (for example, a two-way piston 50 in an embodiment; the same applies hereinafter) that is provided in a fluid pressure control circuit (for example, a hydraulic pressure control circuit HC in the embodiment; the same applies hereinafter), the actuator including a cylinder (for example, a cylinder 51 in the embodiment; the same applies hereinafter), a piston (for example, a piston 52 in the embodiment, the same applies hereinafter) that moves in an axial direction inside the cylinder according to supplied fluid pressure, and a stroke sensor (for example, a stroke sensor 53 in the embodiment, the same applies hereinafter) that detects a position of the piston, wherein an opening (for example, an opening 51 a in the embodiment, the same applies hereinafter) is formed in a circumferential surface of the cylinder, the stroke sensor includes a stay (for example, a stay 53 a in the embodiment, the same applies hereinafter) that is attached to move integrally with the piston and extends from a portion of the piston exposed from the opening to the outside of the cylinder, a magnet (for example, a first magnet 53 b 1 and a second magnet 53 b 2 in the embodiment, the same applies hereinafter) that is attached to a portion of the stay located outside the cylinder, and a sensor (for example, a sensor 53 c in the embodiment, the same applies hereinafter) that detects a position of the magnet, and the magnet is located at a position away from the opening.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustrative diagram schematically illustrating a vehicle on which a transmission including an actuator according to an embodiment is mounted.

FIG. 2 is a skeleton diagram illustrating a transmission mounted on the vehicle of FIG. 1.

FIG. 3 is an alignment chart of a planetary gear mechanism of the transmission in FIG. 2.

FIG. 4 is an illustrative view illustrating an engagement state of each engagement mechanism in each gear stage of the transmission in FIG. 2.

FIG. 5 is a sectional view illustrating a locked state of the two-way clutch illustrating of the transmission in FIG. 2.

FIG. 6 is a cross-sectional view illustrating a reverse rotation prevention state of a main part of the two-way clutch of the transmission in FIG. 2.

FIG. 7 is a perspective view illustrating a locked state of the two-way clutch of the transmission in FIG. 2.

FIG. 8 is a perspective view illustrating a reverse rotation prevention state of the two-way clutch of the transmission in FIG. 2.

FIG. 9A and FIG. 9B is are illustrative diagrams illustrating a switching control mechanism that performs switching of a two-way clutch of a transmission in FIG. 2, FIG. 9A illustrates a case in which the two-way clutch is set to a locked state, and FIG. 9B illustrates a case in which the two-way clutch is set to a reverse rotation prevention mode.

FIG. 10 is a perspective view illustrating shapes of a piston, a stay, a magnet, and a sensor of a two-way piston which is the switching control mechanism of FIG. 9A and FIG. 9B.

FIG. 11 is a plan view of the two-way piston of FIG. 10.

DESCRIPTION OF THE EMBODIMENTS

An actuator of the disclosure is an actuator (for example, a two-way piston 50 in an embodiment; the same applies hereinafter) that is provided in a fluid pressure control circuit (for example, a hydraulic pressure control circuit HC in the embodiment; the same applies hereinafter), the actuator including a cylinder (for example, a cylinder 51 in the embodiment; the same applies hereinafter), a piston (for example, a piston 52 in the embodiment, the same applies hereinafter) that moves in an axial direction inside the cylinder according to supplied fluid pressure, and a stroke sensor (for example, a stroke sensor 53 in the embodiment, the same applies hereinafter) that detects a position of the piston, wherein an opening (for example, an opening 51 a in the embodiment, the same applies hereinafter) is formed in a circumferential surface of the cylinder, the stroke sensor includes a stay (for example, a stay 53 a in the embodiment, the same applies hereinafter) that is attached to move integrally with the piston and extends from a portion of the piston exposed from the opening to the outside of the cylinder, a magnet (for example, a first magnet 53 b 1 and a second magnet 53 b 2 in the embodiment, the same applies hereinafter) that is attached to a portion of the stay located outside the cylinder, and a sensor (for example, a sensor 53 c in the embodiment, the same applies hereinafter) that detects a position of the magnet, and the magnet is located at a position away from the opening.

Thus, in the actuator of the disclosure, the magnet of the stroke sensor is located at a position away from the opening of the cylinder via the stay.

Accordingly, a position at which the iron powder gathers is a position away from the opening communicating with the inside of the cylinder, and, therefore, even when the iron powder is attached or attracted to the magnet, the iron powder is prevented from flowing from the opening of the cylinder located upward relative to the magnet into the cylinder.

Therefore, according to the actuator of the disclosure, since the iron powder is prevented from flowing into the cylinder, it is possible to prevent the malfunction of the actuator and the abrasion of the cylinder and the piston due to the iron powder contained in the working fluid.

Further, in the actuator of the disclosure, it is preferable that the cylinder extends in a vertical direction, and the magnet is located below a lower edge portion (for example, a lower edge portion 51 al in an embodiment; the same applies hereinafter) of the opening.

Thus, in the actuator of the disclosure, when the cylinder (that is, the entire actuator) is arranged to extend in the vertical direction, and the magnet of the stroke sensor is arranged below the lower edge portion of the opening of the cylinder via the stay, the iron powder can be more effectively prevented from flowing into the cylinder.

Further, a hydraulic pressure control circuit of the disclosure is a hydraulic pressure control circuit including a two-way piston that switches between a reverse rotation prevention state and a locked state of a two-way clutch (for example, a two-way clutch F1 in an embodiment; the same applies hereinafter), wherein the two-way piston is any one of the actuators.

Further, a fluid pressure control circuit of the disclosure is a fluid pressure control circuit including a parking piston that switches between a parking locked state and a parking released state of a parking lock mechanism, wherein the parking piston is any one of the actuators.

Hereinafter, a vehicle having a transmission including an actuator mounted thereon according to embodiments will be described with reference to the figures.

As illustrated in FIG. 1, an engine E (an internal combustion engine or a driving source) is mounted transversely on the vehicle body so that a crankshaft 1 is directed in a lateral direction of a vehicle body of a vehicle V. A driving force of the engine E is transmitted to a left front wheel WFL, a right front wheel WFR, a left rear wheel WRL, and a right rear wheel WRR via a power transmission device PT.

The power transmission device PT includes a torque converter 2 connected to the crankshaft 1, a transmission 3 connected to the torque converter 2, a front differential gear 4 connected to the transmission 3, a transfer device 5 connected to the front differential gear 4, and a rear differential gear 6 connected to the transfer device 5.

The front differential gear 4 is connected to the left front wheel WFL and the right front wheel WFR via a front left axle 7L and a front right axle 7R. The rear differential gear 6 is connected to the transfer device 5 via a propeller shaft 8, and is connected to the left rear wheel WRL and the right rear wheel WRR via a rear left axle 9L and a rear right axle 9R.

As illustrated in a skeleton diagram of FIG. 2, the transmission 3 includes an input shaft 32 rotatably journaled inside a transmission case 31 (casing), and an output member 33 including an output gear arranged concentrically with the input shaft 32.

A driving force output from the engine E is transmitted to the input shaft 32 via the torque converter 2 having a lock-up clutch and a damper.

Rotation of the output member 33 is transmitted to the left front wheel WFL and the right front wheel WFR (see FIG. 1) via an idle gear 34 that engages with the output member 33, an idle shaft 35 that journals the idle gear 34, a final drive gear 36 journaled on the idle shaft 35, and a final driven gear 41 (that is, the front differential gear 4) that engages with the final drive gear 36.

In the power transmission device PT, a single plate type or multiple plate type of starting clutch configured to be frictionally engageable may be provided instead of the torque converter 2.

Inside the transmission case 31, a first planetary gear mechanism PG1, a second planetary gear mechanism PG2, a third planetary gear mechanism PG3, and a fourth planetary gear mechanism PG4 are arranged concentrically with the input shaft 32 in this order from the engine E side.

The third planetary gear mechanism PG3 is configured as a so-called single pinion type planetary gear mechanism having, as elements, a sun gear Sc, a ring gear Rc, and a carrier Cc that rotatably and revolvably journals a pinion Pc that engages with the sun gear Sc and the ring gear Rc.

The so-called single pinion type planetary gear mechanism is also called a minus planetary gear mechanism or a negative planetary gear mechanism because the ring gear rotates in a direction different from that of the sun gear when the carrier is fixed and the sun gear is rotated. In the so-called single pinion type planetary gear mechanism, when the ring gear is fixed and the sun gear is rotated, the carrier rotates in the same direction as the sun gear.

An alignment chart (a diagram capable of representing ratios between relative rotational speeds of three elements including the sun gear, the carrier, and the ring gear using straight lines (speed lines)) illustrated in a second part from the top in FIG. 3 is an alignment chart of the third planetary gear mechanism PG3. As illustrated in this alignment chart, when the sun gear Sc, the carrier Cc, and the ring gear Rc that are three elements of the third planetary gear mechanism PG3 are a 1st element, a 2nd element, and a 3rd element from the left in an arrangement order at intervals corresponding to the gear ratio (number of teeth of the ring gear/number of teeth of the sun gears) in the alignment chart, respectively, the 1st element is the sun gear Sc, the 2nd element is the carrier Cc, and the 3rd element is the ring gear Rc.

Here, a ratio between an interval from the sun gear Sc to the carrier Cc and an interval from the carrier Cc to the ring gear Rc is set to h:1 when a gear ratio of the third planetary gear mechanism PG3 is h. In the alignment chart, a lower horizontal line and an upper horizontal line (lines overlapping 4th and 6th) indicate that rotational speeds are “0” and “1” (the same rotational speed as the input shaft 32), respectively.

The fourth planetary gear mechanism PG4 is also configured as a so-called single pinion type planetary gear mechanism including, as elements, a sun gear Sd, a ring gear Rd, and a carrier Cd that rotatably and revolvably journals the pinion Pd that engages with the sun gear Sd and the ring gear Rd.

An alignment chart illustrated at a first row (a top row) from the top in FIG. 3 is an alignment chart of the fourth planetary gear mechanism PG4. As illustrated in this alignment chart, when the sun gear Sd, the carrier Cd, and the ring gear Rd that are three elements of the fourth planetary gear mechanism PG4 are a 4th element, a 5th element, and a 6th element from the left in an arrangement order at intervals corresponding to the gear ratio in the alignment chart, respectively, the 4th element is the ring gear Rd, the 5th element is the carrier Cd, and the 6th element is the sun gear Sd.

Here, a ratio between an interval from the sun gear Sd to the carrier Cd and an interval from the carrier Cd to the ring gear Rd is set to i:1 when a gear ratio of the fourth planetary gear mechanism PG4 is i.

The first planetary gear mechanism PG1 is also configured as a so-called single pinion type planetary gear mechanism having, as elements, a sun gear Sa, a ring gear Ra, and a carrier Ca that rotatably and revolvably journals the pinion Pa meshed with the sun gear Sa and the ring gear Ra.

An alignment chart illustrated at a third row from the top in FIG. 3 is an alignment chart of the first planetary gear mechanism PG1. As illustrated in this alignment chart, when the sun gear Sa, the carrier Ca, and the ring gear Ra that are three elements of the first planetary gear mechanism PG1 are a 7th element, an 8th element, and a 9th element from the left in an arrangement order at intervals corresponding to the gear ratio in the alignment chart, respectively, the seventh element is the sun gear Sa, the eighth element is the carrier Ca, and the ninth element is the ring gear Ra.

Here, a ratio between an interval from the sun gear Sa to the carrier Ca and an interval from the carrier Ca to the ring gear Ra is set to j:1 in which a gear ratio of the first planetary gear mechanism PG1 is j.

The second planetary gear mechanism PG2 is also a so-called single pinion type planetary gear mechanism that includes, as elements, a sun gear Sb, a ring gear Rb, and a carrier Cb that rotatably and revolvably journals a pinion Pb meshing with the sun gear Sb and the ring gear Rb.

An alignment chart illustrated at a fourth row (a bottom row) from the top in FIG. 3 is an alignment chart of the second planetary gear mechanism PG2. As illustrated in this alignment chart, when the sun gear Sb, the carrier Cb, and the ring gear Rb that are three elements of the second planetary gear mechanism PG2 are a 10th element, an 11th element, and a 12th element from the left in an arrangement order at intervals corresponding to the gear ratio in the alignment chart, respectively, the 10th element is the ring gear Rb, the 11th element is the carrier Cb, and the 12th element is the sun gear Sb.

Here, a ratio between an interval from the sun gear Sb to the carrier Cb and an interval from the carrier Cb to the ring gear Rb is set to k:1 in which a gear ratio of the second planetary gear mechanism PG2 is k.

The sun gear Sc (a first element) of the third planetary gear mechanism PG3 is connected to the input shaft 32. Further, the ring gear Rb (a tenth element) of the second planetary gear mechanism PG2 is connected to the output member 33 that includes an output gear.

Further, the carrier Cc (a second element) of the third planetary gear mechanism PG3, the carrier Cd (a fifth element) of the fourth planetary gear mechanism PG4, and the ring gear Ra (a ninth element) of the first planetary gear mechanism PG1 are connected to one another to constitute a first connection body Cc-Cd-Ra.

Further, the ring gear Rc (a third element) of the third planetary gear mechanism PG3 and the sun gear Sb (a twelfth element) of the second planetary gear mechanism PG2 are connected to constitute the second connection body Rc-Sb.

Further, the carrier Ca (the eighth element) of the first planetary gear mechanism PG1 and the carrier Cb (the eleventh element) of the second planetary gear mechanism PG2 are connected to each other to constitute a third connection body Ca-Cb.

Further, the transmission 3 includes seven engagement mechanisms that include three clutches including a first clutch C1, a second clutch C2, and a third clutch C3, three brakes including a first brake B1, a second brake B2, and a third brake B3, and a one two-way clutch F1.

The first clutch C1 is a hydraulically actuated wet multi-plate clutch. Using the first clutch C1, the third planetary gear mechanism PG3 is configured to be switchable between a connection state in which the sun gear Sc (the first element) is connected to the third connection body Ca-Cb and an open state in which this connection is released.

The third clutch C3 is a hydraulically actuated wet multi-plate clutch. Using the third clutch C3, the third planetary gear mechanism PG3 is configured to be switchable between a connection state in which the sun gear Sc (the first element) is connected to the ring gear Rd (the fourth element) of the fourth planetary gear mechanism PG4 and an open state in which this connection is released.

The second clutch C2 is a hydraulically actuated wet multi-plate clutch. Using the second clutch C2, the fourth planetary gear mechanism PG4 is configured to be switchable between a connection state in which the sun gear Sd (the sixth element) is connected to the second connection body Rc-Sb and an open state in which this connection is released.

The two-way clutch F1 also functions as the fourth brake B4. This two-way clutch F1 is configured to be switchable between a reverse rotation prevention state in which forward rotation (rotation in the same direction as a rotation direction of the input shaft 32 and the output member 33) of the third connection body Ca-Cb is allowed and reverse rotation is prevented and a locked state in which the third connection body Ca-Cb is fixed to the transmission case 31.

The two-way clutch F1 is allowed to rotate and enters the open state when a force to rotate the third connection body Ca-Cb in the forward rotation direction is applied to the third connection body Ca-Cb in the reverse rotation prevention state. On the other hand, when a force to rotate the third connection body Ca-Cb in the reverse rotation direction is applied to the third connection body Ca-Cb, the two-way clutch F1 enters the locked state in which the rotation is prevented and the third connection body Ca-Cb is fixed to the transmission case 31.

The first brake B1 is a hydraulically actuated wet type multi-plate brake. With the first brake B1, the first planetary gear mechanism PG1 is configured to be switchable between a locked state in which the sun gear Sa (the seventh element) is fixed to the transmission case 31, and an open state in which this fixing is released.

The second brake B2 is a hydraulically actuated wet type multi-plate brake. With the second brake B2, the fourth planetary gear mechanism PG4 is configured to be switchable between a locked state in which the sun gear Sd (the sixth element) is fixed to the transmission case 31, and an open state in which this fixing is released.

The third brake B3 is a hydraulically actuated wet type multi-plate brake. With the third brake B3, the fourth planetary gear mechanism PG4 is configured to be switchable between a locked state in which the ring gear Rd (the fourth element) is fixed to the transmission case 31, and an open state in which this fixing is released.

Switching of the three clutches including the first clutch C1, the second clutch C2, and the third clutch C3, the three brakes including the first brake B1, the second brake B2, and the third brake B3, and the one two-way clutch F1 is controlled on the basis of vehicle information such as a traveling speed of the vehicle V that is transmitted from an integrated control unit (not illustrated) or the like by the control unit ECU (see FIG. 1) including a transmission control unit (TCU).

The control unit ECU is configured as an electronic unit including a CPU, a memory, and the like (not illustrated). The control unit ECU receives predetermined vehicle information such as a traveling speed or an accelerator opening degree of the vehicle V, a rotational speed or an output torque of the engine E, and information on an operation of a paddle shift lever, and executes a control program stored in a storage device such as a memory using the CPU to control the transmission 3.

In the transmission 3, the first clutch C1, the first planetary gear mechanism PG1, the second planetary gear mechanism PG2, the third planetary gear mechanism PG3, the second clutch C2, the fourth planetary gear mechanism PG4, and the third clutch C3 are arranged on an axis of the input shaft 32 in order from the engine E and the torque converter 2 side.

The third brake B3 is arranged radially outward from the fourth planetary gear mechanism PG4, the second brake B2 is arranged radially outward from the second clutch C2, the first brake B1 is arranged radially outward from the first clutch C1, and the two-way clutch F1 is arranged radially outward from the first planetary gear mechanism PG1.

Therefore, in the transmission 3, the first brake B1, the second brake B2, the third brake B3, and the two-way clutch F1 are arranged radially outward from the planetary gear mechanism or the clutch. Accordingly, an axial length of the transmission 3 is shorter as compared with a case in which the first brake B1, the second brake B2, the third brake B3, and the two-way clutch F1 are arranged side by side on the axis of the input shaft 32 together with the planetary gear mechanism.

When the third brake B3 can be arranged radially outward from the third clutch C3 and the second brake B2 can be arranged radially outward from the fourth planetary gear mechanism PG4, it is possible to similarly achieve shortening.

Here, a case in which each gear stage of the transmission 3 of the embodiment is established will be described with reference to FIGS. 3 and 4.

A speed line indicated by a broken line in FIG. 3 indicates that, following a planetary gear mechanism that transmits power among the first planetary gear mechanism PG1, the second planetary gear mechanism PG2, the third planetary gear mechanism PG3, and the fourth planetary gear mechanism PG4, each of elements of other planetary gear mechanisms rotates (idle).

FIG. 4 is a diagram is a combination of states of three clutches including the first clutch C1, the second clutch C2, and the third clutch C3, three brakes including the first brake B1, the second brake B2, and the third brake B3, and one two-way clutch F1 in each gear stage which will be described below.

In FIG. 4, “O” in columns of the first clutch C1, the second clutch C2, the third clutch C3, the first brake B1, the second brake B2, and the third brake B3 indicates the connection state or the locked state, and a blank indicates the open state. Further, “R” in the column of the two-way clutch F1 indicates a reverse rotation prevention state, and “L” indicates the locked state.

Further, underlined “R” and “L” indicate that the rotational speed of the third connection body Ca-Cb has become “0” due to action of the two-way clutch F1. Further, “R/L” indicates “R” in the reverse rotation prevention state in the normal state, but switching to “L” in the locked state when the engine brake is applied.

Further, FIG. 4 illustrates a gear ratio of each gear stage (rotational speed of the input shaft 32/rotational speed of the output member 33), and a common ratio (a ratio of gear ratios between respective gear stages. A value obtained by dividing a gear ratio of a predetermined gear stage by a gear ratio of a gear stage that is one stage higher than a predetermined gear stage) when a gear ratio h of the third planetary gear mechanism PG3 is 2.734, a gear ratio i of the fourth planetary gear mechanism PG4 is 1.614, a gear ratio j of the first planetary gear mechanism PG1 is 2.681, and a gear ratio k of the second planetary gear mechanism PG2 is 1.914. It can be seen from this that the common ratio can be set appropriately.

When the first gear stage is established, the two-way clutch F1 is set to the reverse rotation prevention state (R in FIG. 4), and the first brake B1 and the second brake B2 are set to a locked state.

By setting the two-way clutch F1 to the reverse rotation prevention state (R) and the first brake B1 to the locked state, the reverse rotation of the third connection body Ca-Cb and the sun gear Sa (the seventh element) of the first planetary gear mechanism PG1 is prevented, and the rotational speed of the third connection body Ca-Cb and the sun gear Sa (the seventh element) of the first planetary gear mechanism PG1 becomes “0”.

Accordingly, the sun gear Sa (the seventh element), the carrier Ca (the eighth element), and the ring gear Ra (the ninth element) of the first planetary gear mechanism PG1 enter a locked state in which relative rotation is impossible, and the rotational speed of the first connection body Cc-Cd-Ra including the ring gear Ra (the ninth element) of the first planetary gear mechanism PG1 also becomes “0”.

The rotational speed of the ring gear Rb (the tenth element) of the second planetary gear mechanism PG2 to which the output member 33 is connected becomes “1st” illustrated in FIG. 3, and the first gear stage is established.

In order to establish the first gear stage, it is not necessary to set the second brake B2 to the locked state. However, it is set to the locked state at the first gear stage in order to smoothly shift from the first gear stage to the second gear stage to be described below. Further, when an engine brake is applied at the first gear stage, the two-way clutch F1 may be switched from the reverse rotation prevention state (R) to the locked state (L).

When the second gear stage is established, the two-way clutch F1 is set to the reverse rotation prevention state (R), the first brake B1 and the second brake B2 are set to the locked state, and the second clutch C2 is set to a connection state.

By setting the two-way clutch F1 to the reverse rotation prevention state, the forward rotation of the third connection body Ca-Cb is allowed. Further, by setting the first brake B1 to the locked state, the rotational speed of the sun gear Sa (the seventh element) of the first planetary gear mechanism PG1 becomes “0”. Further, by setting the second brake B2 to the locked state, the rotational speed of the sun gear Sd (the sixth element) of the fourth planetary gear mechanism PG4 becomes “0”.

Further, by setting the second clutch C2 to the connection state, the rotational speed of the second connection body Rc-Sb becomes “0”, which is the same speed as the rotational speed of the sun gear Sd (the sixth element) of the fourth planetary gear mechanism PG4.

The rotational speed of the ring gear Rb (the tenth element) of the second planetary gear mechanism PG2 to which the output member 33 is connected becomes “2nd” illustrated in FIG. 3, and the second gear stage is established.

When the third gear stage is established, the two-way clutch F1 is set to the reverse rotation prevention state, the first brake B1 and the second brake B2 are set to the locked state, and the third clutch C3 is set to a connection state.

By setting the two-way clutch F1 to the reverse rotation prevention state, the forward rotation of the third connection body Ca-Cb is allowed. Further, by setting the first brake B1 to the locked state, the rotational speed of the sun gear Sa (the seventh element) of the first planetary gear mechanism PG1 becomes “0”. Further, by setting the second brake B2 to the locked state, the rotational speed of the sun gear Sd (the sixth element) of the fourth planetary gear mechanism PG4 becomes “0”.

Further, by setting the third clutch C3 to the connection state, the rotational speed of the ring gear Rd (the fourth element) of the fourth planetary gear mechanism PG4 becomes “1”, which is the same speed as the rotational speed of the sun gear Sc (the first element) of the third planetary gear mechanism PG3 connected to the input shaft 32.

Accordingly, since the rotational speed of the sun gear Sd (the sixth element) of the fourth planetary gear mechanism PG4 becomes “0” and the rotational speed of the ring gear Rd (the fourth element) becomes “1”, the rotational speed of the carrier Cd (the fifth element), that is, the rotational speed of the first connection body Cc-Cd-Ra is i/(i+1).

The rotational speed of the ring gear Rb (the tenth element) of the second planetary gear mechanism PG2 to which the output member 33 is connected becomes “3rd” illustrated in FIG. 3, and the third gear stage is established.

When the 4th gear stage is established, the two-way clutch F1 is set to the reverse rotation prevention state, the first brake B1 is set to the locked state, and the second clutch C2 and the third clutch C3 are set to a connection state.

By setting the two-way clutch F1 to the reverse rotation prevention state, the forward rotation of the third connection body Ca-Cb is allowed. Further, by setting the first brake B1 to the locked state, the rotational speed of the sun gear Sa (the seventh element) of the first planetary gear mechanism PG1 becomes “0”.

Further, by setting the second clutch C2 to the connection state, the sun gear Sd (the sixth element) of the fourth planetary gear mechanism PG4 and the second connection body Rc-Sb rotate at the same speed. Accordingly, between the third planetary gear mechanism PG3 and the fourth planetary gear mechanism PG4, the carrier Cc (the second element) and the carrier Cd (the fifth element) are connected and the ring gear Rc (the third element) and the sun gear Sd (the sixth element) are connected. Therefore, in the 4th gear stage in which the second clutch C2 is connected, one alignment chart including four elements can be drawn by the third planetary gear mechanism PG3 and the fourth planetary gear mechanism PG4.

Further, by setting the third clutch C3 to the connection state, the rotational speed of the ring gear Rd (the fourth element) of the fourth planetary gear mechanism PG4 becomes “1” that is the same as the rotational speed of the sun gear Sc (the first element) of the third planetary gear mechanism PG3, and the rotational speeds of two elements among the four elements configured by the third planetary gear mechanism PG3 and the fourth planetary gear mechanism PG4 become “1” which is the same speed.

Accordingly, the respective elements of the third planetary gear mechanism PG3 and the fourth planetary gear mechanism PG4 enter a locked state in which relative rotation is impossible, and the rotational speeds of all the elements of the third planetary gear mechanism PG3 and the fourth planetary gear mechanism PG4 become “1”. Further, the rotational speed of the third connection body Ca-Cb becomes j/(j+1).

The rotational speed of the ring gear Rb (the tenth element) of the second planetary gear mechanism PG2 to which the output member 33 is connected becomes “4th” illustrated in FIG. 3, and the 4th gear stage is established.

When the 5th gear stage is established, the two-way clutch F1 is set to the reverse rotation prevention state, the first brake B1 is set to the locked state, and the first clutch C1 and the third clutch C3 are set to the connection state.

By setting the two-way clutch F1 to the reverse rotation prevention state, the forward rotation of the third connection body Ca-Cb is allowed. Further, by setting the first brake B1 to the locked state, the rotational speed of the sun gear Sa (the seventh element) of the first planetary gear mechanism PG1 becomes “0”.

Further, by setting the first clutch C1 to the connection state, the rotational speed of the third connection body Ca-Cb becomes “1” which is the same speed as the rotational speed of the sun gear Sc (the first element) of the third planetary gear mechanism PG3.

The rotational speed of the ring gear Rb (the tenth element) of the second planetary gear mechanism PG2 to which the output member 33 is connected becomes “5th” illustrated in FIG. 3, and the fifth gear stage is established.

In order to establish the 5th gear stage, it is not necessary to set the third clutch C3 to the connection state. However, in the 4th gear stage and the 6th gear stage to be described below, since it is necessary to set the third clutch C3 to the connection state, the connection state is set in the 5th gear stage so that downshift from the 5th gear stage to the 4th gear stage and upshift from the 5th gear stage to the 6th gear stage to be described below are smoothly performed.

When the 6th gear stage is established, the two-way clutch F1 is set to the reverse rotation prevention state, and the first clutch C1, the second clutch C2, and the third clutch C3 are set to the connection state.

By setting the two-way clutch F1 to the reverse rotation prevention state, the forward rotation of the third connection body Ca-Cb is allowed.

Further, by setting the second clutch C2 and the third clutch C3 to the connection state, the respective elements of the third planetary gear mechanism PG3 and the fourth planetary gear mechanism PG4 enter a locked state in which the relative rotation is impossible, and the rotational speed of the second connection body Rc-Sb becomes “1”, as described in the description of the 4th gear stage. Further, by setting the first clutch C1 to the connection state, the rotational speed of the third connection body Ca-Cb becomes “1”.

Accordingly, the carrier Cb (the eleventh element) and the sun gear Sb (the twelfth element) of the second planetary gear mechanism PG2 become the same speed “1”, and the respective elements enter the locked state in which relative rotation is impossible.

The rotational speed of the ring gear Rb (the tenth element) of the second planetary gear mechanism PG2 to which the output member 33 is connected becomes “1” of “6th” illustrated in FIG. 3, and the 6th gear stage is established.

When the seventh gear is established, the two-way clutch F1 is set to the reverse rotation prevention state, the second brake B2 is set to the locked state, and the first clutch C1 and the third clutch C3 are set to the connection state.

By setting the two-way clutch F1 to the reverse rotation prevention state, the forward rotation of the third connection body Ca-Cb is allowed. Further, by setting the second brake B2 to the locked state, the rotational speed of the sun gear Sd (the sixth element) of the fourth planetary gear mechanism PG4 becomes “0”.

Further, by setting the third clutch C3 to the connection state, the rotational speed of the ring gear Rd (the fourth element) of the fourth planetary gear mechanism PG4 becomes “1” which is the same speed as the rotational speed of the sun gear Sc (the first element) of the third planetary gear mechanism PG3, and the rotational speed of the first connection body Cc-Cd-Ra including the carrier Cd (the fifth element) of the fourth planetary gear mechanism PG4 becomes i/(i+1). Further, by setting the first clutch C1 to the connection state, the rotational speed of the third connection body Ca-Cb becomes “1” that is the same speed as the rotational speed of the sun gear Sc (the first element) of the third planetary gear mechanism PG3 connected to the input shaft 32.

The rotational speed of the ring gear Rb (the tenth element) of the second planetary gear mechanism PG2 to which the output member 33 is connected becomes “7th” illustrated in FIG. 3, and the seventh gear stage is established.

When the 8th gear stage is established, the two-way clutch F1 is set to the reverse rotation prevention state, the second brake B2 is set to the locked state, and the first clutch C1 and the second clutch C2 are set to the connection state.

By setting the two-way clutch F1 to the reverse rotation prevention state, the forward rotation of the third connection body Ca-Cb is allowed. Further, by setting the second brake B2 to the locked state, the rotational speed of the sun gear Sd (the sixth element) of the fourth planetary gear mechanism PG4 becomes “0”.

Further, by setting the second clutch C2 to the connection state, the rotational speed of the second connection body Rc-Sb becomes “0” which is the same speed as the rotational speed of the sun gear Sd (the sixth element) of the fourth planetary gear mechanism PG4. Further, by setting the first clutch C1 to the connection state, the rotational speed of the third connection body Ca-Cb becomes “1” which is the same speed as the rotational speed of the sun gear Sc (the first element) of the third planetary gear mechanism PG3.

The rotational speed of the ring gear Rb (the tenth element) of the second planetary gear mechanism PG2 to which the output member 33 is connected becomes “8th” illustrated in FIG. 3, and the 8th gear stage is established.

When the 9th gear stage is established, the two-way clutch F1 is set to the reverse rotation prevention state, the second brake B2 and the third brake B3 are set to the locked state, and the first clutch C1 is set to the connection state.

By setting the two-way clutch F1 to the reverse rotation prevention state, the forward rotation of the third connection body Ca-Cb is allowed. Further, by setting the second brake B2 to the locked state, the rotational speed of the sun gear Sd (the sixth element) of the fourth planetary gear mechanism PG4 becomes “0”. Further, by setting the third brake B3 to the locked state, the rotational speed of the ring gear Rd (the fourth element) of the fourth planetary gear mechanism PG4 also becomes “0”.

Accordingly, the sun gear Sd (the sixth element), the carrier Cd (the fifth element), and the ring gear Rd (the fourth element) of the fourth planetary gear mechanism PG4 enter the locked state in which relative rotation is impossible, and the rotational speed of the first connection body Cc-Cd-Ra including the carrier Cd (the fifth element) of the fourth planetary gear mechanism PG4 is also “0”.

Further, by setting the first clutch C1 to the connection state, the rotational speed of the third connection body Ca-Cb becomes “1” which is the same speed as the rotational speed of the sun gear Sc (the first element) of the third planetary gear mechanism PG3.

The rotational speed of the ring gear Rb (the tenth element) of the second planetary gear mechanism PG2 to which the output member 33 is connected becomes “9th” illustrated in FIG. 3, and the 9th gear stage is established.

When the 10th gear stage is established, the two-way clutch F1 is set to the reverse rotation prevention state, the third brake B3 is set to the locked state, and the first clutch C1 and the second clutch C2 are set to the connection state.

By setting the two-way clutch F1 to the reverse rotation prevention state, the forward rotation of the third connection body Ca-Cb is allowed. Further, by setting the third brake B3 to the locked state, the rotational speed of the ring gear Rd (the fourth element) of the fourth planetary gear mechanism PG4 becomes “0”.

Further, by setting the second clutch C2 to the connection state, the second connected body Rc-Sb and the sun gear Sd (the sixth element) of the fourth planetary gear mechanism PG4 rotate at the same speed. Further, by setting the first clutch C1 to the connection state, the rotational speed of the third connection body Ca-Cb becomes “1” which is the same speed as the rotational speed of the sun gear Sc (the first element) of the third planetary gear mechanism PG3.

The rotational speed of the ring gear Rb (the tenth element) of the second planetary gear mechanism PG2 to which the output member 33 is connected becomes “10th” illustrated in FIG. 3, and the 10th gear stage is established.

When the reverse stage is established, the two-way clutch F1 is set to the locked state (L in FIG. 4), the second brake B2 is set to the locked state, and the third clutch C3 is set to the connection state.

By setting the second brake B2 to the locked state and setting the third clutch C3 to the connection state, the rotational speed of the first connection body Cc-Cd-Ra becomes i/(i+1). Further, by setting the two-way clutch F1 to the locked state, the rotational speed of the third connection body Ca-Cb becomes “0”.

The rotational speed of the ring gear Rb (the tenth element) of the second planetary gear mechanism PG2 to which the output member 33 is connected becomes “Rvs” which is reverse rotation illustrated in FIG. 3, and the reverse stage is established.

Next, the two-way clutch F1 will be described in detail with reference to FIGS. 5 to 8.

The two-way clutch F1 is configured to be switchable between a locked state in which the third connection body Ca-Cb is fixed to the transmission case 31 and a reverse rotation preventions state in which forward rotation of the third connected body Ca-Cb is allowed and reverse rotation thereof is prevented.

As illustrated in cross section in FIGS. 5 and 6, the two-way clutch F1 includes a fixed plate TW11 fixed in the transmission case 31, and a rotation plate TW12.

As illustrated in FIG. 7, the fixed plate TW11 is formed in an annular shape (a donut shape). Although not illustrated in FIG. 7, the rotation plate TW12 is also formed in an annular shape (a donut shape) similar to the fixed plate TW11, and the fixed plate TW11 and the rotation plate TW12 are arranged concentrically.

As illustrated in FIG. 5, a plate-shaped forward rotation prevention side swing portion TW13, and a plate-like reverse rotation prevention side swing portion TW14 are provided on a first opposing surface TW11 a of the fixed plate TW11 facing the rotation plate TW12.

The forward rotation prevention side swing portion TW13 is attached to the fixed plate TW11 so that a first end portion TW13 a on the other circumferential side (a direction in which the rotation plate TW12 rotates in a reverse direction) can be swung using an end portion on one circumferential side of the fixed plate TW11 (a direction in which the rotation plate TW12 rotates in a forward direction) as an axle.

The reverse rotation prevention side swing portion TW14 is attached to the fixed plate TW11 so that a second end portion TW14 a on one circumferential side (a forward rotation direction) can be swung using an end portion on the other circumferential side of the fixed plate TW11 (a reverse rotation direction) as an axle.

Further, a first reception portion TW15 recessed to be able to receive the forward rotation prevention side swing portion TW13, and a second reception portion TW16 recessed to be able to receive the reverse rotation prevention side swing portion TW14 are provided in the first opposing surface TW11 a of the fixed plate TW11.

A first biasing member TW17 a made of a spring that biases the forward rotation prevention side swing portion TW13 is provided on a bottom surface of the first reception portion TW15 so that the swinging first end portion TW13 a of the forward rotation prevention side swing portion TW13 protrudes from the first reception portion TW15.

A second biasing member TW17 b made of a spring that biases the reverse rotation prevention side swing portion TW14 is provided on a bottom surface of the second reception portion TW16 so that the swinging second end portion TW14 a of the reverse rotation prevention side swing portion TW14 protrudes from the second reception portion TW16.

On a second opposing surface TW12 a of the rotation plate TW12 facing the fixed plate TW11, a first hole TW18 is provided at a position corresponding to the forward rotation prevention side swing portion TW13, and a second hole TW19 is provided at a position corresponding to the reverse rotation prevention side swing portion TW14.

In the first hole TW18 provided at the position corresponding to the forward rotation prevention side swing portion TW13, a first engagement portion TW18 a having a step shape that is located on the other circumferential side (reverse rotation direction side) of the rotation plate TW12 and is engageable with the swinging first end portion TW13 a of the forward rotation prevention side swing portion TW13 is provided.

In the second hole TW19 provided at the position corresponding to the reverse rotation prevention side swing portion TW14, a second engagement portion TW19 a having a step shape that is located on one circumferential side (forward rotation direction side) of the rotation plate TW12 and is engageable with the swinging second end portion TW14 a of the reverse rotation prevention side swing portion TW14 is provided.

As illustrated in FIGS. 5 and 7, when the first end portion TW13 a of the forward rotation prevention side swing portion TW13 and the first engagement portion TW18 a can be engaged with each other, and the second end portion TW14 a of the reverse rotation prevention side swing portion TW14 and the second engagement portion TW19 a can be engaged with each other, both the forward rotation and the reverse rotation of the rotation plate TW12 is prevented. Therefore, a state in which the first end portion TW13 a and the second end portion TW14 a and the first engagement portion TW18 a and the second engagement portion TW19 a corresponding thereto are engaged with each other becomes a locked state in the two-way clutch F1.

A switching plate TW20 is sandwiched between the fixed plate TW11 and the rotation plate TW12. The switching plate TW20 is also formed in an annular shape (a donut shape). A first notch hole TW20 a and a second notch hole TW20 b are provided at positions corresponding to the forward rotation prevention side swing portion TW13 and the reverse rotation prevention side swing portion TW14 in the switching plate TW20. At an outer edge of the switching plate TW20, a protrusion portion TW20 c protruding outward in a radial direction is provided.

As illustrated in FIG. 8, the switching plate TW20 is freely rotatable with respect to the fixed plate TW11.

When the switching plate TW20 is swung from the locked state illustrated in FIG. 7 to the state illustrated in FIG. 8, the first notch hole TW20 a corresponding to the forward rotation prevention side swing portion TW13 moves to exceed the forward rotation prevention side swing portion TW13, as illustrated in FIG. 6. The forward rotation prevention side swing portion TW13 is pressed against the switching plate TW20 and is accommodated in the first reception portion TW15 against the force of the first biasing member TW17 a.

Accordingly, engagement of the first end portion TW13 a of the forward rotation prevention side swing portion TW13 with the first engagement portion TW18 a is prevent, and the rotation on the forward rotation side of the rotation plate TW12 is allowed.

Further, as illustrated in FIG. 8, the second notch hole TW20 b corresponding to the reverse rotation prevention side swing portion TW14 is configured such that the second end portion TW14 a can be engaged with the second engagement portion TW19 a without the reverse rotation prevention side swing portion TW14 accommodated in the second reception portion TW16 even when the switching plate TW20 is swung from the locked state illustrated in FIG. 7 to the state illustrated in FIG. 8.

From these facts, the states illustrated in FIGS. 6 and 8 become the reverse rotation prevention state in the two-way clutch F1.

Next, a switching control mechanism for performing switching of the two-way clutch F1 will be described with reference to FIG. 9A and FIG. 9B.

As illustrated in FIG. 9A and FIG. 9B, a hydraulic pressure control circuit HC (fluid pressure control circuit) provided in the transmission 3 includes a piston HC1 that is engaged with the protrusion portion TW20 c provided in the switching plate TW20. The two-way clutch F1 is switched to the locked state when the piston HC1 moves to a predetermined position (a position illustrated in FIG. 9A) on the left side illustrated in FIG. 9A and FIG. 9B, and is switched to the reverse rotation prevention state when the piston HC1 moves to a predetermined position (a position illustrated in FIG. 9B) on the right side illustrated in FIG. 9A and FIG. 9B.

On the right side of the piston HC1 in the figure, a line pressure can be freely supplied via a first opening and closing valve HC2 including a solenoid valve. On the left side of the piston HC1 in the figure, a line pressure can be freely supplied via a second opening and closing valve HC3 including a solenoid valve. The first opening and closing valve HC2 is a normally closed type, and the second opening and closing valve HC3 is a normally open type.

The first opening and closing valve HC2 and the second opening and closing valve HC3 are opened and closed according to a signal from the control unit ECU. That is, the two-way clutch F1 is controlled by the control unit ECU via the hydraulic pressure control circuit HC.

On the right side of the piston HC1 in the figure, hydraulic pressure (fluid pressure) to be supplied to the third clutch C3 is supplied to a surface different from a surface receiving the line pressure. On the left side of the piston HC1 in the figure, hydraulic pressure to be supplied to the first clutch C1, the first brake B1, or the second brake B2 is supplied to a surface different from a surface receiving the line pressure. The hydraulic pressures of the first clutch C1, the first brake B1 or the second brake B2, and the third clutch C3 supplied to the piston HC1 are used as RVS preparatory pressure.

Further, a detent mechanism HC4 is provided in the piston HC1 and is configured so that switching between the locked state illustrated in FIG. 9A and the reverse rotation prevention state illustrated in FIG. 9B does not occur unless the line pressure exceeds a predetermined value.

According to this hydraulic pressure control circuit HC, the piston HC1 moves to the left side in the figure and the two-way clutch F1 is switched to the locked state by setting the line pressure to be equal to or higher than predetermined switching hydraulic pressure by opening the first opening and closing valve HC2 and closing the second opening and closing valve HC3. The predetermined switching hydraulic pressure is set on the basis of a pressure difference between the hydraulic pressure of the first clutch C1, the first brake B1, or the second brake B2 and the hydraulic pressure of the third clutch C3 and a load due to the first elastic member 54 a and the second elastic member 54 b constituting the detent mechanism HC4.

Conversely, the piston HC1 moves to the right side in the figure and the two-way clutch F1 is switched to the reverse rotation prevention state by setting the line pressure to be equal to or higher than the predetermined switching hydraulic pressure described above by closing the first opening and closing valve HC2 and opening the second opening and closing valve HC3.

Next, the two-way piston 50 (actuator) that is used as a switching control mechanism will be described with reference to FIGS. 10 and 11. In FIG. 11, a flow of working oil including iron powder is indicated by an arrow. Further, a vertical direction in FIG. 11 matches a vertical direction of the power transmission device PT (that is, the hydraulic pressure control circuit HC of the transmission 3) mounted on the vehicle V.

As illustrated in FIGS. 10 and 11, the two-way piston 50 includes a cylindrical cylinder 51, a piston 52 that moves in a direction of the axis “a” inside the cylinder 51 according to the supplied hydraulic pressure, a stroke sensor 53 that detects a position of the piston 52, and a detent mechanism 54 that fixes the position of the piston 52 until the hydraulic pressure exceeds a predetermined value.

The cylinder 51 is integrally formed with a case of the hydraulic pressure control circuit HC, and an opening 51 a communicating the inside and the outside of the cylinder 51 is formed in a center portion of a circumferential surface thereof.

The piston 52 is connected to the protrusion portion TW20 c of the two-way clutch F1 via a link structure (not illustrated). Therefore, according to a reciprocating motion of the piston 52 in the direction of the axis “a”, the protrusion portion TW20 c also performs a reciprocating motion, and switching between the locked state and the reverse rotation prevention state of the two-way clutch F1 occurs.

The piston 52 is configured by a member having a substantially cylindrical shape. On a side surface of the piston 52, a pair of first concave portions 52 a provided to face each other with the axis “a” interposed therebetween, and a pair of second concave portions (not illustrated. These are located on the first plate-like portion 53 al of the stay 53 a to be described below) provided to face each other with the axis “a” interposed therebetween on the lower side (the side of a stay 53 a described below) relative to the first concave portion 52 a are formed.

A stroke sensor 53 includes a stay 53 a attached to move integrally with the piston 52 and extending from a portion of the piston 52 exposed from an opening 51 a to the outside of the cylinder 51, a member to be detected 53 b attached to a portion of the stay 53 a located outside the cylinder 51, and a sensor 53 c that detects a position of the member to be detected 53 b (eventually, the position of the piston 52).

The stay 53 a is a L-shaped member including a first plate-like portion 53 al which is fixed to intersect the axis “a” in the portion of the piston 52 exposed from the opening 51 a, and a second plate-like portion 53 a 2 which extends downwardly from an end portion opposite to the piston 52 side of the first plate-like portion 53 al. The stay 53 a is fixed to the piston 52 by fastening a central portion of the first plate-like portion 53 al to the piston 52 with a bolt 53 a 3.

The member to be detected 53 b is fixed to a distal end portion of the second plate-like portion 53 a 2 of the stay 53 a opposite to the first plate-like portion 53 al side. A first magnet 53 b 1 and a second magnet 53 b 2 are arranged on the side of the sensor 53 c of the member to be detected 53 b. The first magnet 53 b 1 is located on the first cutout 53 al side (an upper side in a vertical direction) of the stay 53 a in the direction of the axis “a” relative to the second magnet 53 b 2.

The sensor 53 c detects a magnetic force (eventually, a position of the member to be detected 53 b) of the first magnet 53 b 1 and the second magnet 53 b 2 of the member to be detected 53 b. The control unit ECU (see FIG. 1) determines the position of the piston 52 (eventually, a state of the two-way clutch F1 controlled by the two-way piston 50) on the basis of a detection value transmitted from the sensor 53 c, and controls the hydraulic pressure that is supplied to the two-way piston 50 on the basis of a result of the determination.

The detent mechanism 54 includes a pair of elastic members (a first elastic member 54 a and a second elastic member 54 b) that are arranged to face each other with the axis “a” interposed therebetween and presses the piston 52 to sandwich the piston 52 therebetween.

The first elastic member 54 a and the second elastic member 54 b are engaged with any one of the pair of first concave portions 52 a and the pair of second concave portions formed on the side surface of the piston 52 when the piston 52 is located at any one of a position corresponding to the locked state and a position corresponding to the reverse rotation prevention state of the two-way clutch F1 to fix the position of the piston 52. Specifically, the detent mechanism 54 is engaged with the second concave portion in the state illustrated in FIG. 10, and is engaged with the first concave portion 52 a in the state illustrated in FIG. 11.

This fixing is released when the hydraulic pressure applied to the piston 52 exceeds a predetermined value (specifically, the predetermined switching hydraulic pressure is set on the basis of the pressure difference between the hydraulic pressure of the first clutch C1, the first brake B1 or the second brake B2 and the hydraulic pressure of the third clutch C3 and the load due to the first elastic member 54 a and the second elastic member 54 b constituting the detent mechanism 54).

Incidentally, in the hydraulic pressure control circuit HC in which the two-way piston 50 is provided, working oil including iron powder generated by the abrasion of the engagement mechanism such as the first clutch C1 may flow on a surface of the casing. Therefore, there is concern that the iron powder may be attached or attracted to the first magnet 53 b 1 and the second magnet 53 b 2 of the stroke sensor 53, and may flow into the cylinder 51 when the piston 52 moves.

Thus, when the iron powder flows into the cylinder 51, there is concern that a malfunction such as hindrance of the stroke of the piston 52 may occur or abrasion of the cylinder 51 and the piston 52 may occur.

Therefore, in the two-way piston 50, the first magnet 53 b 1 and the second magnet 53 b 2 are designed to be located below the lower edge portion 51 al of the opening 51 a of the cylinder 51 in order to prevent the iron powder from flowing into the cylinder 51.

Specifically, when the piston 52 moves downward according to a state of the two-way clutch F1 (when a state illustrated in FIG. 11 is reached), both of the first magnet 53 b 1 and the second magnet 53 b 2 are located below the lower edge portion 51 a 1. On the other hand, when the piston 52 moves upward (when a state illustrated in FIG. 10 is reached), the second magnet 53 b 2 located further downward between the first magnet 53 b 1 and the second magnet 53 b 2 is located below the lower edge portion 51 al.

Accordingly, a position at which the iron powder gathers is a position below the lower edge portion 51 al of the opening 51 a communicating with the inside of the cylinder 51 (see the arrow indicating the flow of the working oil in FIG. 11), and, therefore, even when the iron powder is attached or attracted to the first magnet 53 b 1 and the second magnet 53 b 2, the iron powder is prevented from flowing from the opening 51 a of the cylinder 51 located above the first magnet 53 b 1 and the second magnet 53 b 2 into the cylinder 51.

Therefore, according to the two-way piston 50, since the iron powder is prevented from flowing into the cylinder 51, it is possible to prevent the malfunction of the two-way piston 50 and abrasion of the cylinder 51 and the piston 52 due to the iron powder contained in the working oil.

Although the embodiments shown in the drawings have been described above, the disclosure is not limited to such embodiments.

For example, in the above embodiment, the actuator of the disclosure is adopted as the two-way piston 50 for switching between the locked state and the reverse rotation prevention state of the two-way clutch F1. However, the actuator of the disclosure is not an actuator that can be adopted only for such a two-way piston. For example, the actuator of the disclosure may be adopted as a parking piston that switches between a parking locked state and a parking released state of the parking lock mechanism.

Further, in the above embodiment, when the cylinder 51 is arranged to extend in the vertical direction and the piston 52 is located on the lower side, the actuator may be configured so that both of the first magnet 53 b 1 and the second magnet 53 b 2 are located below the lower edge portion 51 al, and the second magnet 53 b 2 located further downward between the first magnet 53 b 1 and the second magnet 53 b 2 is located below the lower edge portion 51 a 1 when the piston 52 is located on the upper side.

However, an arrangement direction of the cylinder and a positional relationship between the magnet and the opening in the disclosure are not limited to such a configuration, and the magnet may be located at a position away from the opening of the cylinder.

For example, the actuator may be configured so that only the magnet on one side (that is, at least some of the magnets) is located below the lower edge portion of the opening regardless of the position of the piston. The actuator may be configured so that all the magnets are always located below the lower edge portion of the opening. Further, the actuator may be configured so that the magnet is located at a position away from the opening in a horizontal direction. 

What is claimed is:
 1. An actuator that is provided in a fluid pressure control circuit of a transmission, the actuator comprising: a cylinder; a piston that moves in an axial direction inside the cylinder according to a supplied fluid pressure; and a stroke sensor that detects a position of the piston, wherein an opening is formed in a circumferential surface of the cylinder, the stroke sensor includes a stay that is attached to move integrally with the piston and extends from a portion of the piston exposed from the opening to the outside of the cylinder, a magnet that is attached to a portion of the stay located outside the cylinder, and a sensor that detects a position of the magnet, and the magnet is located at a position away from the opening.
 2. The actuator according to claim 1, wherein the cylinder extends in a vertical direction, and the magnet is located below a lower edge portion of the opening.
 3. A hydraulic pressure control circuit comprising a two-way piston that switches between a reverse rotation prevention state and a locked state of a two-way clutch, wherein the two-way piston is the actuator according to claim
 1. 4. A hydraulic pressure control circuit comprising a two-way piston that switches between a reverse rotation prevention state and a locked state of a two-way clutch, wherein the two-way piston is the actuator according to claim
 2. 5. A fluid pressure control circuit comprising a parking piston that switches between a parking locked state and a parking released state of a parking lock mechanism, wherein the parking piston is the actuator according to claim
 1. 6. A fluid pressure control circuit comprising a parking piston that switches between a parking locked state and a parking released state of a parking lock mechanism, wherein the parking piston is the actuator according to claim
 2. 